Astronomy:Super-puff

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Short description: Planet with a mass slightly above Earth but with a radius larger than Neptune
Super-puff planet-bpk.png

A super-puff is a type of exoplanet with a mass only a few times larger than Earth's but with a radius larger than that of Neptune, giving it a very low mean density.[1] They are cooler and less massive than the inflated low-density hot-Jupiters.[1]

The most extreme examples known are the three planets around Kepler-51 which are all Jupiter-sized but with densities below 0.1 g/cm3.[1] These planets were discovered in 2012 but their low densities were not discovered until 2014.[2] Another example is Kepler-87c.[1]

One hypothesis is that a super-puff has continuous outflows of dust to the top of its atmosphere (for example, Gliese 3470 b)- so the apparent surface is really dust at the top of the atmosphere.[2] Another possibility is that some of the super-puff planets are smaller planets with large ring systems, like HIP 41378 f.[3]

References